


Little Big Sister

by Sunnybone



Series: Sylver AU Fics [1]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Angst, Crestless!Sylvain, Experiment!Sylvain, Mentions of past child abuse, The shipping is implied, because Sylvain, because TWSITD, mentions of experimentation, pre-Conand Tower
Language: English
Status: Completed
Published: 2020-03-18
Updated: 2020-03-18
Packaged: 2021-02-28 22:22:09
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,744
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23194672
Author URL: https://archiveofourown.org/users/Sunnybone/pseuds/Sunnybone
Summary: Sylvain, born without a Crest but bearing one nonetheless, is close with Lysithea von Ordelia after coming to the Academy. It's easier to be friends with her than the trio of Faerghus nobles he knew as a young child, especially Felix.Based on@vwyn19's absolutely devastating Crest Experiment Sylvain AU comic and inspired byHe Willby TK_DuVeraun
Relationships: Felix Hugo Fraldarius/Sylvain Jose Gautier, Sylvain Jose Gautier & Lysithea von Ordelia
Series: Sylver AU Fics [1]
Series URL: https://archiveofourown.org/series/1700455
Comments: 14
Kudos: 292





	Little Big Sister

**Author's Note:**

> Waen's Crestless Sylvain comic emotionally beat my ass behind a Denny's, and then TK made me think about Sylvain and Lysithea being friends, and really I'm just consumed at all times with Sylvain Angst Brainworms so I had no choice but to try my hand at this AU.

She wants to get rid of her Crests.

Sylvain understands that, because Lysithea's only fifteen, just a little _girl_ , with a whole life ahead of her if she can manage it.

Sylvain only has Gautier and the border, and probably a marriage as loveless as the one his parents have, and _his parents_. There's nothing he wants to live for, so if he dies young from his Crest, so be it.

He doesn't say as much to Lysithea, but she's smart. She understands the difference in their circumstances. Her family wept while she and her siblings were cut apart and driven mad and made inhuman; _Sylvain's_ father had only complained at the lack of progress on Miklan, and offered Sylvain up to strangers eager to prove their experiments a second time.

She also understands that there's no one else he can turn to, no one else who _understands_ like she does. Edelgard, perhaps, they muse, but Sylvain doesn't trust her like he trusts Lysithea. Lysithea is a child, with childish secrets, and Edelgard is a princess—her secrets are deadly, they have teeth, and Sylvain knows enough about that to keep his wary distance.

So Lysithea wants to get rid of her Crests, and she works so _hard_ for it. Personally, if Sylvain had the luxury of a family who loved him, he wouldn't be wasting what time he has at the Academy, spending every waking moment studying spells and glyphs and magical theorems that may never even pan out. He doesn't bother bringing it up, though, because he knows Lysithea is too smart not to realize. It's obvious from her desperation that she _knows_ it's unlikely she'll ever find a solution.

It makes her snappy, but Sylvain never takes it to heart when she complains that he doesn't take their burden seriously enough, doesn't try hard enough. Lysithea is _smart_ , but she's still a _child_ ; she hasn't realized yet that Sylvain doesn't _at all_ share her desire to live any longer than his Gautier Crest will allow, is not interested in clawing even one more second from his wrecked body. It's a knowledge that would hurt her, he thinks, and that's one thing he's determined _not_ to do.

They've both been hurt enough, already.

Instead, he helps her pore over books and practice spells and test out theorems when he’s not in classes with the lions, and it’s a bit of a relief. It’s nice to spend time with her and know that the only eyes on him are speculating about why he’s so chummy with a _little girl_ when everyone knows what a flirt he is. Flirt, if they’re being polite; more often he catches the curl of ‘ _slut_ ’ on gossiping lips, and ‘ _whore_ ’ on the less charitable ones.

Sex is mindless physicality with a dual purpose—it takes his mind off of existing, for just a little while, and it keeps his parents from dragging him home and marrying him off and chaining him to a bed until he produces a precious heir to keep their line from being cut short. Not that he’s taking any chances of creating bastards, but his _parents_ don’t need to know about his preventative measures, his herbal concoctions and charms.

Anyways.

It’s nice to only have the usual eyes glaring him down like a pervert, instead of staring with concerned confusion at his snowy hair and his inky fingers and the pale scars crawling up his arms and chest that he pointedly doesn’t try to hide.

Ingrid and Dimitri are blatant in their concern, and that makes it easy to rebuff, to redirect—oh look, another use for the sex, something for Ingy and Dima to focus on and try to fix, because they have no _idea_ what’s happened to him and _no_ idea how to deal with it. 

Ingrid goes behind him, dealing with all the girls who didn’t quite understand that Sylvain wasn’t looking for anything serious, anything _real_ , and he sees her wondering what happened to the boy who used to listen to her go on about knight tales while they braided horse manes. Dimitri tries several times, awkwardly, to have genuine conversations about his behavior, which Sylvain easily deflects with innuendos and pretends not to see the _disappointment_ in Dimitri’s eyes, Sylvain falling from the Older Brother Friend pedestal to smash at its base.

Felix, though.

Felix watches. Felix snarks and snipes and complains just as much as anyone about Sylvain’s _habits_ , but his stares are different. They’re careful, concealed, none of that open concern and dismay, just… assessing. Like if he glares long enough and hard enough when he thinks no one else can see him, he’ll find some answer to whatever question Sylvain presents.

Somehow, the quiet scrutiny from the kid who used to rub snot on his shirt from crying over every tiny hurt is so much harder to deal with than Ingrid and Dimitri. Their reactions make sense. Felix, standoffish and prickly and barely _speaking_ to Dimitri, is as different from the child Sylvain remembers as he supposes he is himself.

Sylvain _vastly_ prefers the judgmental eyes of strangers over the weighing looks from someone he’d once been close enough to to promise they’d die together.

Not that he can keep that kind of promise anymore.

He shifts in his seat, next to Lysithea at a library table piled with books and notes written in both their neat hands, drawings of Glyphs with careful annotations beneath formulae they’ve solved. They’ve been here since dinner, which Sylvain insisted on (“an empty stomach is diminished mental capacity, ‘Sith”), and as the library had cleared a bit he had slipped her a little bag of sugar candies.

The secrecy is silly, in his opinion, but he’d been good enough at humoring his friends when they were all children, and he can humor Lysithea now. She wants to be seen as mature and adult, because she didn’t have the luxury of a childhood and may never _be_ an adult; Sylvain treats her like an adult, for the most part, though he still secretly delights in the simple joy on her face when given sweets. 

Lysithea is mumbling about the flavor of a purple-wrapped candy and tapping her quill along an equation when the doors open and Felix, of all people, slips inside.

Lysithea scrambles to hide the candies, as if that’s not horrifically suspicious, and Felix of _course_ notices. He looks at Lysithea’s guilty face, the bag she has just haphazardly shoved the candies and half of her books into, and then at Sylvain with narrowing eyes. Sylvain snorts.

“It’s fine, ‘Sith; he’s not gonna steal your candies, y’know. Felix hates sweets.” Lysithea hisses at him, but Sylvain only lifts his eyebrows until she groans and starts digging the books back out of her bag.

She turns to glare at Felix, who looks unimpressed. “Tell _no one_ about this.” He rolls his eyes.

“Sure, because I live to gossip.” Felix turns his attention back to Sylvain, arms crossed. “Come spar with me; you’ve been avoiding training and you’re going to gather dust with all these books.” Lysithea makes a disgruntled little noise, and Sylvain leans back in his seat, slinging a lazy arm across the back as he looks up at Felix.

He keeps telling Felix he’s a mage now, and yet Felix keeps pressing him to pick up a lance and go toe-to-toe. Sylvain’s not sure if it’s out of a desire for something familiar from Newly Strange Sylvain, or an attempt to limit his magic use and thus the slow darkening of his fingers—something he’s caught Felix’s puzzled stare on more than once. Maybe it’s a bit of both.

He wouldn't mind sparring with Felix, honestly, just another kind of mindless physicality, and a lot less messy—in every sense—than sex. Actually, to be _very_ honest, slightly _preferable_ to sex.

"I dunno, Felix," he says, turning Felix's name into something almost sing-song, "I've already promised my evening to Lysithea's tutelage. Maybe if you ask her nicely she'll loan me out." He tilts his head towards Lysithea, who is looking annoyed at the interruption. "What d'you say, Big Sis—am I training my brain or my brawn tonight?" He already knows before he finishes asking that she's going to throw him out. She hates when he calls her his _big_ sister, jokingly; everyone else might think he's mocking her age, or her size, or her tendency towards bossiness, but they _both_ know it's a comment on their Crests. She'd been a success, so he'd been a success, a test of adding a Crest to a base vessel instead of ' _improving'_ an already superior subject.

"You might as _well_ go hit each other with sticks, if you can't take this _seriously_ ," she says, which is as good as telling him to _get the fuck out_ , and Sylvain chuckles over Felix's offended little snort and quickly arranges the mess of his books and notes for her, knowing she'll use them while he's gone.

"Sure, sure, but you could at least worry about Felix bashing my big pretty brain in." She doesn't dignify that with more than a narrowing of her eyes—big and pink, so that she looks to him sometimes like the fluffy rabbits bred and kept in Gautier for their soft wool. It always reminds him how small she is, how young, and he will never voice it for fear of her wrath but he feels protective of her. It's stupid, because the worst things in her life had already happened before they'd met, but he still tries a smile. "Don't stay up too late, huh?"

"I'm perfectly capable of managing my own schedule, _Sylvain_." Which is as good as telling him _shut the fuck up_ , and that she'll probably stay up past a reasonable hour and wind up exhausted. His smile turns into a smirk.

"Oh, that's good, since you wouldn't want to be _alone_ in the library too late." He reaches out, hooks two fingers through a lock of her long hair, and gives the tiniest playful tug. "After all, I've heard it's _haunted_." As he stands and drapes a scarred arm across Felix's shoulders—quickly thrown off, but that's the usual—and steers him towards the doors, Lysithea only sputters behind them about how only children are afraid of _ghosts_ and they aren't _real_ anyways.

Sylvain feels confident she'll make an early night of it.

**Author's Note:**

> Thanks so much for reading!
> 
> Find me on twitter at [@AceMorningStar](https://twitter.com/AceMorningStar)


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